Miles Hawk Speed Sixes G-ADOD and G-ACTE

[Methuselah]

Ratier Adapter; - Here is the sketch repeated below, showing the Ratier adapter that you yourself posted only recently..... The upper image is an SI, the sketch below is an R. The adapter is specifically labelled as such on the R sketch.

Have you omitted, as an attachment, the sketch to which you refer?

The lower sketch clearly showing the Ratier adapter fitted onto the No.1 Splines of the R. Labelled 'Extended crankshaft for Ratier airscrew'. The arrow somewhat misleadingly pointing to the cutaway area - but patently referring to the adapter which sleeved-over the splined end the the R's crankshaft.

 

[steelpillow]

Ratier Adapter; - Here is the sketch repeated below, showing the Ratier adapter that you yourself posted only recently..... The upper image is an SI, the sketch below is an R. The adapter is specifically labelled as such on the R sketch.

Have you omitted, as an attachment, the sketch to which you refer?

The lower sketch clearly showing the Ratier adapter fitted onto the No.1 Splines of the R. Labelled 'Extended crankshaft for Ratier airscrew'. The arrow somewhat misleadingly pointing to the cutaway area - but patently referring to the adapter which sleeved-over the splined end the the R's crankshaft.

Except, the text does not identify the spline as a No.1 type. In fact it is of the type used in the US for the contemporary heavy Hamilton-Standard V-P props.

The Series II crankshaft was to the UK standard and, as you can see from the attached, its spline was rather shorter and less meaty, tailored to the reduced power of the Gipsy Six. Some other design changes mentioned in the text, made to shaft and housing, were also absent from the R.

Given the amount of space dedicated to the mistake on this thread, I think it important that this be made clear.

Note too the forged and domed piston also introduced on the II. I wonder if Jack Cross "borrowed" a set for Henshaw's R, rather than rustle up his own design.

 

[steelpillow]

Seems the American splines are standardised by the SAE. The SAE10, 20, 30... splines correspond fairly closely to the SBAC 1, 2, 3... but they are not interchangeable. This causes much grief when, say, looking for a prop for a restored R-R Merlin vs. license-built Packard V-1650. But the earliest SAE standard I can find is 1942. Back in 1935 the standards were still being made up as they went along, and I can find nothing from that far back.

 

[Methuselah]

Ratier Adapter; - Here is the sketch repeated below, showing the Ratier adapter that you yourself posted only recently..... The upper image is an SI, the sketch below is an R. The adapter is specifically labelled as such on the R sketch.

Have you omitted, as an attachment, the sketch to which you refer?

The lower sketch clearly showing the Ratier adapter fitted onto the No.1 Splines of the R. Labelled 'Extended crankshaft for Ratier airscrew'. The arrow somewhat misleadingly pointing to the cutaway area - but patently referring to the adapter which sleeved-over the splined end the the R's crankshaft.

Except, the text does not identify the spline as a No.1 type. In fact it is of the type used in the US for the contemporary heavy Hamilton-Standard V-P props.

Where does it say this..?

The Series II crankshaft was to the UK standard and, as you can see from the attached,

...a sketch is not a guide for dimensions.

its spline was rather shorter and less meaty, tailored to the reduced power of the Gipsy Six.

Reduced - from what?

Some other design changes mentioned in the text, made to shaft and housing, were also absent from the R.

Given the amount of space dedicated to the mistake on this thread, I think it important that this be made clear.

Note too the forged and domed piston also introduced on the II. I wonder if Jack Cross "borrowed" a set for Henshaw's R, rather than rustle up his own design.

 

[Methuselah]

Note too the forged and domed piston also introduced on the II. I wonder if Jack Cross "borrowed" a set for Henshaw's R, rather than rustle up his own design.

You are presuming that the R pistons weigh the same as the SII pistons..... In any case, Cross was far more likely to have ordered custom pistons from the likes of Hepolite, who were closely involved in supplying parts for racing engines.

 

[steelpillow]

Note too the forged and domed piston also introduced on the II. I wonder if Jack Cross "borrowed" a set for Henshaw's R, rather than rustle up his own design.

You are presuming that the R pistons weigh the same as the SII pistons..... In any case, Cross was far more likely to have ordered custom pistons from the likes of Hepolite, who were closely involved in supplying parts for racing engines.

Wondering is not presuming. Anyway, this is off topic for G-ADOD.

 

[steelpillow]

The different position of the centre of mass of the Ratier is significant - given the moment arm from the CofG. The DH 1000-Series spider (See third photo.) positions the airscrew disc about halfway along the splines, quite close to the front of the engine (See fourth photo.), so the difference (Perhaps 6"+ ..?) is enough, given the mass of the airscrew(s) - metal VP airscrews are heavy assemblies. The PD30/211/1 assembly weighs 70.1 Lbs - the standard spinner weighs another 7.6 Lbs - so 77.7 Lbs total. Remember you have to double the weight as there are two airscrew assemblies - so 155.4 Lbs - all well forward of the CofG. OW, Derby or KF might supply you with the W&B for the Comet so you can work out the effect on the CofG of moving that lot 6". Look again at your photo of the Ratier on the R at OW - it is a significant difference at that weight and moment arm. Did DH act on this issue...? I have no idea.

In 1971 Louis Meurillon wrote a four-part article on the Comet for French magazine L'Album du Fanatique de l'Aviation. Part 2 (Issue 26) gives the weight of the Hamilton props as 54 kg, compared to 25 kg for the Ratier, to which must be added 6 kg for the adapter. Photos suggest that the adapter was about 8 in (20 cm) long, and scale drawings that the whole thing was around 2 M in front of the quarter-chord position (nominal CG). The weight moments of the props are therefore, to a reasonable approximation; Hamilton 54 x 2 = 108 kgM, Ratier 31 x 2.2 = 68 kgM. No amount of nit-picking over errors in estimation can close a gap that big, not even if that 54 kg includes the extra hydraulic supply at the rear of the engine. Overall, the Ratier installation would have shifted the CG back not forwards.

 

[Methuselah]

I don't have a weight to hand for the Ratier airscrew. I do have a Ratier manual, but I can't lay my hand on it at the moment. I'll have a look for it next week, but I'm pretty sure it quotes a weight. However - the PD30/211/1 is an anglicised DH copy of the HS Bracket Airscrew. The hub might weigh a bit more or less than the versions test-fittled to the Comet. DH's later altered the blade design a tad. However - to get from 70.1 Lbs/31.8kg (As per the the DH manual.) - to 119.05 Lbs/54kg is quite a leap - a 48 Lbs/22.20 kg leap to precisely 'nit-pick'. Possible..? Maybe. Probable...? No. Where is DeHavs figure for the HS airscrew weight...? Some obscure magazine article doesn't pass muster. Were the spinners and all of the actuation mechanism included for both airscrews?

Do you have the DH data on the splines on the R crankshaft - because that would be a very interesting nugget - no matter which splines were used. It'll be interesting to see if another genuine R has turned-up - if it has the same crankshaft splines as the one at OW. Perfectly useless information - but interesting nonetheless - even if it is off-topic.

- Cheers.

 

[steelpillow]

to get from 70.1 Lbs/31.8kg (As per the the DH manual.) - to 119.05 Lbs/54kg is quite a leap - a 48 Lbs/22.20 kg leap

Yes. This was precisely why DH were so worried about the risks of the heavy American props that they instituted a backup plan. That backup was the one which found its way onto the operational planes and hence also into the manual. The saga is well documented by many commentators, both contemporary and subsequent.

Do you have the DH data on the splines on the R crankshaft - because that would be a very interesting nugget - no matter which splines were used. It'll be interesting to see if another genuine R has turned-up - if it has the same crankshaft splines as the one at OW. Perfectly useless information - but interesting nonetheless - even if it is off-topic.

That documentation has been lost, as far as we know. What we do have is statements that it was made to fit the over-designed Hamiltons, and an example at Shuttleworth which may still retain them under its adapter sleeve. Whether G-ADOD's engine survives, and whether it was cut down for the bracket flange, are the only aspects which are in fact relevant to the present topic.

On that last, it occurs to me that the Ratier and Fairey-Reed flanges may even have been compatible, meaning that a Ratier adapter could still have been used. I should have thought of that before.

 

[Methuselah]

to get from 70.1 Lbs/31.8kg (As per the the DH manual.) - to 119.05 Lbs/54kg is quite a leap - a 48 Lbs/22.20 kg leap

Yes. This was precisely why DH were so worried about the risks of the heavy American props that they instituted a backup plan. That backup was the one which found its way onto the operational planes and hence also into the manual. The saga is well documented by many commentators, both contemporary and subsequent.

Do you have the DH data on the splines on the R crankshaft - because that would be a very interesting nugget - no matter which splines were used. It'll be interesting to see if another genuine R has turned-up - if it has the same crankshaft splines as the one at OW. Perfectly useless information - but interesting nonetheless - even if it is off-topic.

That documentation has been lost, as far as we know. What we do have is statements that it was made to fit the over-designed Hamiltons, and an example at Shuttleworth which may still retain them under its adapter sleeve. Whether G-ADOD's engine survives, and whether it was cut down for the bracket flange, are the only aspects which are in fact relevant to the present topic.

On that last, it occurs to me that the Ratier and Fairey-Reed flanges may even have been compatible, meaning that a Ratier adapter could still have been used. I should have thought of that before.

The PD30 wasn't a 'back-up' - it was the basic HS design - shrunk to fit DH's/UK's smaller civil engines - the whole purpose of the agreement with HS from the outset. DH's would have been well aware of the increased mass of any VP design - why would this be a 'risk'..?

As for HS's airscrews being 'over-designed' - well, HS's airscrews were all designed for larger more powerful engines, and - far more importantly, they were designed for radial engines..... The initial blades fitted to the Comet were that same US pattern - and the bladeform didn't extend to the root. The DH bods referred to these as 'Broomstick' blades. This proved to be a big issue. They were less efficient - and the lack of bladeform towards the centre also affected the Gipsy engines cooling. Overall - they didn't offer the efficiency required to give the Comet the required range for the 1934 race. Look at images of the blades as tested - and a PD30, and you'll see how the bladeform on the latter runs close to the spinner.

If you think that DH's used a standard HS assembly - 'off the shelf' to fit to the 'R'- what is the ID for that assembly...as it will still be listed.....? I don't think HS ever made a Bracket-Type VP assembly that small - so good luck with that.


So what do I think happened....? I think that the prototype assemblies made for the Comets were to the HS design - and DH's specs - including the spider. Given the very short time available - they may have been made - at least in part in the US. I think the blades carried HS transfers - so it's a fair bet the blades at least were made in the US. One can imagine them asking HS to make some blades for XYZ RPM/Power?Diameter. (There is a good reason for this;- The blade blanks are forged. The outer shell for the hub's roller-bearings has to be fited onto the blade, outboard of the hub-flange, before the blade is fully-forged.). Had the blades been made in the UK - it's hard to imagine DH's not picking-up on the bladeform issue if they were made locally - a cock-up no doubt resulting from the speed of events.

The Ratier was designed from the outset for engines not equipped for VP operation (ie;- Most small civil engines at that time.) - hence the flanged design - that was the whole point of using the flange. That model - in both variants - was crude - in both fitting and operation. However - it did have the advantage of having an inherently more efficient bladeform - and that was the only reason that DH very reluctantly used them.
As a matter of interest, evidence suggests that given everything else being equal - the PD30's bladeform was never as effective as that used by Ratiers. In all other aspects, the HS design was vastly superior.

DH's fixed pitch engines such as the Six I used a short tapered crankshaft end. Onto this taper, pretty-much any design of fixed-pitch prop hub could be fitted for the many FP airscrew makers. Thus the extended 'adapter' used by the 'R' engines (To clear the splined shafts of the 'R's.) would have been totally unnecessary and the Ratier would have thus sat in the same position as a FP airscrew, therefore, in practice, that extension/adapter would not have been used. "Could have been used' - yes. 'Would have been used' - no, - it would have been pointless.

The whole DH/Ratier preference issue was in evidence in UK domestic and long-distance air-racing/record-setting in 1936 - 1939, and the same basic adapters used on the Comets were also used when Ratiers of that generation were often fitted to Six II's - and for the same reasons.

 

[steelpillow]

The PD30 wasn't a 'back-up' - it was the basic HS design

You misread my statement. The backup plan was the Ratier. You need to re-read my words in that light. Note too that G-ADOD, the subject of this thread, had a Six R and therefore, by default, the heavy Hamilton spline. The question to address is how someone mounted a FP prop, presumably a Fairey-Reed, on it.

So what do I think happened....? ... One can imagine ...

Your version contradicts multiple reliable sources in many ways, large and small. I'd recommend you read up on the known facts before putting too much faith in your own fancies. DH ordered the original props off HS, and Halford splined the Six R crank shaft to accept them. That is documented in great detail in standard reference works such as Sharp's history of de Havilland, Ogilvy's history of the Comet and Taylor's biography of Halford. "One can imagine" all sorts of things, but the facts do speak for themselves.

 

[steelpillow]

The c/n 34 G-ACTE in the Spanish Civil War

Does anybody have any more information about the later career of G-ACTE? It was built for Sir Charles Rose in 1934 and flown in that year's King's Cup. He sold it on to Bill Humble, who raced it for a couple more. It was then "sold abroad" in September 1937. What happened next?

I have seen mention of Spanish sources which say it flew in the Civil War. But who flew it, where, when and why, and what happened to it in the end?

 

[avion ancien]

Peter Amos says that 'CTE left Croydon for Spain on 4 January 1937. He also gives the c/n as 43 rather than 34 (which was Hawk CH-380/HB-OXU).

The answer to your question may lie in one or both of the two books entitled 'Aircraft of the Spanish Civil War 1936 - 39' by (1) Gerald Howson and (2) Carlos Fresno Crespo & Artemio Mortera Pérez - but buying them might prove to be a rather expensive way of discovering that there is no record of 'CTE serving either the Nationalist or Republican forces in the Spanish Civil War!

Addendum: Joaquin Serrano Rubeira in 'British Fighters in the Spanish Civil War' (chap. 7) lists, amongst the foreign aircraft supplied to the Nationalist forces, '1 Miles M.23[sic] Hawk Speed Six' in January 1937.

 

[Arjen]

From Aircraft of the Spanish Civil War 1936-1939 by Gerald Howson, Putnam 1990

The Miles M23 Hawk Speed Six c/n 43, G-ACTE, was a special single-seat racing version of the Hawk Major custom-built for Sir Charles Rose in 1934. It was powered by a 220hp de Havilland Gipsy Six engine and fitted with a sliding, domed cockpit canopy. In 1936 Rose sold it to racing pilot Bill Humble, who, in December, sold it to Stanynought. The sale is dated 4 January 1937, but the machine was out of England by then. Nothing is known of its service with the Republicans beyond a blurred photograph showing what appears to be this aeroplane, standing concealed among trees.

Howson writes Charles Leslie Stanynought, alias L C Lewis

... had been procuring aircraft for Spain since the previous autumn [autumn 1936]

 

[Arjen]

Howson identifies G-ACTE as the M23 Hawk Speed Six.
In Miles Aircraft since 1925 by Don L Brown, Putnam 1970, it is identified as the M.2E Hawk Speed Six.
In British Civil Aircraft 1919-1972: Volume III by A J Jackson, Putnam 1973, G-ACTE is identified as the M.2E Gipsy Six Hawk.

 

[avion ancien]

I suspect that 'M23' is a mistranscription, possibly from an oral account. Reversing a 3 produces an E and 'emm-two-ee' might easily be heard as 'emm-two-three'. Maybe the old 'something lost in translation' issue?